Noncontacting width gauge



April 13, 1954 Filed Jan. 7, 1950 R. E. ANDERSON NONCONTACTING WIDTH GAUGE 6 Shets-Sheec 1 Fi gl.

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' NONCONTACTING WIDTH GAUGE Filed Jan. 7, 1950 6 Sheets-Sheet 2 Fig.2.

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April'l3, 1954 R. E. ANDERSON NONCONTACTING WIDTH GAUGE Filed Jan. 7, 1950 I 6 Sheets-Sheet 5 mmi April 13, 1954 R. E. ANDERSON 2,674,915

NONCONTACTING WIDTH GAUGE Filed Jan. 7, 1950 6 Sheets-Sheet 6 Pi (2.10. a;

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Roy EAnder'son,

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Patented Apr. 13, 1954 NONCONTACTING WIDTH GAUGE Roy E. Anderson, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application January '7, 1950, Serial No. 137,463

8 Claims. 1

This invention relates to noncontacting width gauges, and in particular to width gauges employing electron camera tubes.

Noncontacting gauges are particularly desired for measuring the width of strip material traveling at high speeds and for measuring the width of objects at high temperature. The conditions of measurement are especially severe in steel rolling mills where the Width of hot ingots and hot steel strip is to be measured. In addition to being very hot, the ingots may be moving, sometimes quite erratically. The gauge must be sturdy enough to operate reliably under conditions encountered in rolling mills.

An object of the invention is to provide an improved gauge for indicating the width of hot steel ingots in a rolling mill or for indicating the width of other objects.

The improved noncontacting width gaugescomprise an electron camera, such as an iconoscope, orthicon, or image dissector, which views the hot ingot or other object, the width of which is to be measured. Scanning means are provided for scanning across the width of the cam eras view, whereby the camera provides electric pulses having an average duration which is related to the width of the ingot. Electronic circuits are provided which are responsive to the average duration of these pulses to indicate the width of the ingot.

Other objects and advantages of the invention will appear as the description proceeds. The features of the invention which are believed to be novel and patentable are pointed out in the claims which form a part of this s ecification.

For a better understanding of the invention, reference is made in the following description to the accompanying drawings in which Fig. 1 is a schematic diagram of an improved, noncontacting width gauge; Fig. 2 is a representation of electric waveforms at various points in the Fig. 1 gauge; Fig. 3 is a schematic diagram of another improved noncontacting width gauge; Fig. 4 is a diagram of iconoscope circuits of the Fig. '3

gauge; Fig. 5 is a diagram of synchronizing signal generator circuits of the Fig. 3 gauge; Fig. 6 is a diagram of sweep circuits of the Fig. 3 gauge; Fig. 7 is a circuit diagram of a mixer of the Fig. 3 gauge; Fig. 8 is a diagram of delay circuits of the Fig. 3 gauge; Fig. 9 is a diagram of indicator circuits of the Fig. 3 gauge; and Fig. 10 is a representation of electrical waveforms at various points of the Fig. 3 gauge.

Referring now to Fig. 1, the width of a hot steel ingot l is to be measured. A light sensitive electron-optics device such as an electron camera tube, which is preferably an iconoscope 2, views ingot I through lens 3, as indicated by broken lines 4. The iconoscope, which may be of a conventional type designed for industrial use, has a photosensitive mosaic 5, a cathode 6, a control electrode 1', accelerating electrodes 8, and horizontal beam-deflecting plates 9 and ill. The vertical beam-deflecting plates l l are not necessarily used in this apparatus and could be I omitted. Lens 3 focuses an optical image of ingot i upon photosensitive mosaic 5.

Sweep circuits i2 provide potentials to deflecting plates 9 and It] to scan the electron beam of the iconoscope across the width of the image focused on mosaic 5. As the beam crosses the image, an electric pulse is produced which is related in duration to the width of ingot l, as hereinafter more fully explained. Sweep circuits l2 may also provide a potential to control electrode 7 for blanking during the return sweep of the electron beam and provide a synchronizing signal to trigger circuit l3 through delay circuit 14.

The electric-pulses produced by the iconoscope are amplified by amplifier l5, are added to rectangular waveform pulses from trigger circuit l3, and after passing through clipping circuit It control the gating of a gated oscillator ll. Oscillator ll provides oscillations at a fixed frequency but is'biased so that it is inoperative to provide such oscillations except during times when pulses are received from clipping circuit H5. The oscillations provided by oscillator I! are fed into a cycle counter i6 which responds to the numb r of cycles of such oscillations provided during each pulse produced by the iconoscope electron beam being swept across the ingot image and thereby indicates the width of ingot l.

Operation of the Fig. 1 apparatus can be better understood by reference to the electric waveforms represented in Fig. 2. Referring to Figs. 1 and 2, curve I9 represents potential applied to deflecting plate 9, and curve 26 represents potential applied to deflecting plate Iii, The electron beam of the iconoscope is periodically swept across the width of mosaic 5 during portions 25 of the sweep potentials l9 and 28. During portions 22 of the sweep potentials, the beam is returned to its initial position.

The potential applied to control electrode E is represented by curve 23. During the forward sweep (2|) of the electron beam, a positive potential 24 is applied to the control electrode which intensifies the beam during the forward sweep.

During the return sweep (22), negative potential 25 is applied to electrode 1, which cuts off or blanks the beam. Sweep circuits [2 may be of the type illustrated in Fig. 6, hereinafter described, or may be other sweep circuits known in the art which provide the desired waveforms. If the Fig. 6 circuit is used in this embodiment of the invention, the trigger circuit comprising vacuum tubes i8! and 83 may be modified to operate as a free-running multivibrator; or, the Fig. 6 circuit may be used without modification and driven by a suitable oscillator or pulse generator.

Again referring to Figs. 1 and, 2, curve 26 represents the voltages produced at rnosaiet as the electron beam is swept across the mosaic. The extremities of the sweep may extend somewhat beyond the mosaic edges. One or more initial pulses 27, of relatively short duration, occur shortly after the sweep begins when the electron beam first strikes the mosaic. A relatively long pulse 28 produced as the beam crosses the image of ingot t. A series of relatively short pulses 29- may be produced at the end of the sweep as the beam passes the edge of the mosaic. The small irregularities in curve Zirepresent --noise voltages which are inherently present.

Trigger circuit [3, which may be of the conventional type commonly called a one-shot mul-ti-vibrator, provides a rectangular waveform pulse of predetermined duration .each time circuit I3 is triggered by the sweep circuits through delay circuit [4, which may be similar to one half of the-delay circuits illustrated in Fig. 8, hereinafter described. Gircuit 14 provides an impulse to trigger circuit 13 shortly after each sweep begins, and the constants of circuit 53 are arranged so that its output. pulse terminates shortly beforethe sweep ends. Thus, the output of trigger circuit [3 consists of a series of rectangular waveform pulses as indicated by curve 30.

The voltages represented by curves 26 and 36 are added together at the input of clipping circuit l8 and thus provide at the input of the clipping circuit the voltage waveform represented by curve 31. Clipping circuit is may be of a conventional type which transmits only those voltage values which exceed in amplitude the pulses, shown in curve 30, supplied by the trigger circuit. Thus, pulses 28 only are transmitted through the clipping circuit, and pulses 21 and 29 are blocked, as illustrated by curve 32. The pulses 28 are then applied to gated oscillator I! and turn the oscillator on for the duration of these pulses.

Curve 33 represents electric oscillations pro vided by gated oscillator H. The oscillations 34 have a fixed frequency, but the oscillator is biased so that oscillations are provided only during the pulses 28. The number of oscillations .34 which occur during .each iconoscope sweep is therefore proportional to the width of pulses 28 and hence to the width of ingot l. These oscillations 34 actuate cycle counter I8, which thereupon indicates the width of ingot l. Oscillator I! and cycle counter 18 may be conventional apparatus which is well known in the art.

In the apparatus illustrated in Fig. l, variations in the distance between ingot I and the iconoscope may afiect the width indication since such variations obviously affect the relation between the width of ingot l and the width of the image focused upQn mosaic 5. Such variations in distance are quite likely to occur in a steel rolling mill where the hot in ots sometimes 4 buckle and bounce by considerable amounts during the rolling process and where the ingots may also vary in thickness. Preferred apparatus which substantially overcomes this difliculty and also provides greater sensitivity to small width changes is shown in Fig. 3.

Referring now to Fig. 3, the width of a hot ingot 35 is to be measured. Two electron light sensitive electron-optics devices which may comprise cameras such as iconoscopes 3i; and 37 are employed. It will be appreciated that other electron Camera tubes, such as orthicons or image clissectors, may be employed in place of the iconoscopes and that the circuit modifications necessary to accommodate these different fields of view of the two iconosoopes are represented by broken lines 44 and 35, respectively. Each of the two electron-optics devices formed by the iconoscopes 35 and 31 are positioned so that the optical axis of the field of view thereof (indicated by dotted lines 440; and did) is vertically aligned with a respective associated edge of the ingot. By this arrangement then, erroneous indications of width deviations .due to up and down vibrations or bucking of the ingot, are

* minimized.

Separate sweep circuits 4t and 47 are provided for the two iconoscopes. These sweep circuits are synchronized by a signal generator 48 so that the two partial images are scanned alternately. Iconoscopes 36 and 3'! thus alternately produce electric pulses, the widths of which are related to the widths of the partial images formed on the respective iconoscope mosaics.

As the apparatus is generally used, there is a standard .or desired ingot width, deviations from which are to be indicated. The two iconoscopes 3t and 3? are preferably spaced apart a distance equal to this desired width so that iconoscope 36 is normally directly above one edge of ingot 35 while iconoscope 3! is directly above the other edge. With this arrangement, any buckling or up or down motion of the ingot does not substantially affect the sizes of the partial images formed upon the iconoscope mosaics, and hence does not substantially affect the width indication. Any lateral motion of the ingot increases the width of one partial image but decreases the width of the other partial image by a corresponding amount so that the average width of the two partial images, and hence the width indication as hereinafter explained, is not substantially affected. Deviations from the desired width, however, cause variations in the average width of the two partial images and hence are indicated.

The pulses produced by iconoscopes 3B and 3! are combined in a mixer 49 and then actuate indicator circuits 50. Delay circuits 5! are provided to block undesired pulses which are produced when the electron beam of an iconoscope enters the mosaic, as is hereinafter more fully explained. To facilitate an understanding of how the various circuits are connected together, the connections in Fig. 3 are labeled with the same reference numerals as in the circuit diagrams shown in Figs. 4-9.

Refer now to Fig. 4 which illustrates in more detail typical electrical circuits for one of the iconoscope cameras. Since the two cameras may have identical circuits, only one is described.

The iconoscope 35, which may be a conventional type designed for industrial use, has a photosensitive mosaic 40, a cathode 52, a control electrode 53, accelerating electrodes 54, horizontal deflection plates 55 and. 55, and vertical deflection plates 51. Operating potentials for the cathode, control electrode, and one or more of the accelerating electrodes may be suppliedfrom taps on a voltage divider 58 which is connected to a suitable source of negative direct voltage, minus one thousand volts being a suitable value for at least one type of iconoscope.

Horizontal deflecting plates 55 and 55 are connected to adjustable taps on a voltage divider 59 which may be connected to a source of positive direct voltage, plus 300 volts, for example. The adjustable taps of voltage divider 59 permit adjustment of the steady state potentials applied to plates 55 and 55 which adjust the position of the iconoscope electron beam during times when no sweep potentials are applied. Potentials for sweeping the beam across mosaic 40 to scan an image are applied to plates 55 and 55 by the sweep circuits through connections 55 and 5|. Blanking voltage is applied to the control electrode through connection 52.

Vertical deflecting plates 51 are connected to adjustable taps on voltage divider 63 which is connected to a suitable source of positive voltage. These adjustable taps permit adjustment of the vertical position of the iconoscope electron beam. Although sweep potentials need not be applied to the vertical deflecting plates, since vertical scanning is unnecessary in this apparatus, high frequency vertical sweep voltage is preferably applied through capacitors 64 and 55 and connections 55 and 51, as hereinafter explained.

A microammeter 58 may be connected to one or more of the accelerating electrodes 54, as shown, to facilitate adjustment of the operating potentials of the iconoscope. This is conventional and requires no further description. Voltage pulses produced when the image on masaic 40 is scanned are applied to the mixer through connection 69.

Referring now to Fig. 5, the synchronizing signal generator 48 may be a conventional free running multivibrator. In a preferred form, the signal generator comprises two triodes and 1| having plate load resistors 12 and 13, respectively. The control electrodes of the two vacuum tubes 10 and 1| are connected through resistors 14 and 15 to taps of voltage dividers 15 and 11, respectively, which are connected between a positive voltage source and ground. Feedback connections are provided from the plate of tube 1| to a tap on resistor 14 through capacitor 18, and from the plate of tube 10 to a tap on resistor 15 through capacitor 19. This multivibrator operates in a well-known manner to provide voltages to the two sweep circuits through connections 80 and 8|. The waveforms of these two voltages are represented in Fig. 10 by curves 82 and 83, respectively.

Refer now to Fig. 6 which shows a preferred form of the horizontal sweep circuits 45, 41.

Since the twosets of horizontal sweep circuits may be identical, only one will be described. The

voltage waveform illustrated at 82, Fig. 10, is

supplied by the signal generator through connection 80. This voltage is differentiated by capacitor 84 and resistor 85 so that a series of relatively short voltage pulses, represented in Fig. vl0 by curve 86, are applied to the control electrode of a vacuum tube 81. Tube 81 is connected with another vacuum tube 88 in a cathode coupled trigger circuit. The cathodes of these two vacuum tubes are connected together, as shown, and are connected to ground through a common cathode resistor 89. The plates are connected to a suitable source of positive direct voltage through load resistors 99 and 9i, respectively. The control electrode of tube 81 is connected to a voltage divider comprising resistors 92 and. 85 connected in series between the positive voltage source and ground. The potential of this control electrode is such that tube 81 is normally cut off when tube 88 conducts current. The control electrode of tube 88 is connected to the positive voltage source through a resistor 93 and is connected to the plate of tube 8'! through a capacitor 94.

In this trigger circuit the control electrode of tube 88 is normally at a relatively high positive potential, and tube 88 conducts current. This produces a voltage drop across cathode resistor 89 which is suflicient to keep tube 81 cut off. When a positive voltage pulse, such as a pulse 95, Fig. 10, is applied'to the control electrode of tube 81, this tube conducts current and the potential of its plate drops. This drop in potential drives the control grid of tube 88 negative and cuts off the tube. Tube 81 continues to conduct current as long as tube 88 is cut off. However, capacitor 94 receives current through resistor Y93, and the control electrode of tube 88 gradually becomes more positive. After a time, depending upon the values of resistor 93 and capacitor 94, tube 88 again conducts current and cuts off tube 81. The result is a rectangular voltage pulse represented at 95, Fig. 10, at the plate of tube 81. These pulses 96 are initiated each time a pulse is applied to the control electrode of tube 81, which may be at a rate of 10 to 30 per second, depending upon the frequency of the synchronizing signal generator. The duration of pulses 95 is uniform since it is determined by the values of resistor 99 and capacitor 94. This duration may be 0.0005 second, for example.

Pulses 95 are applied through a capacitor 91 to a bootstrap sweep generator comprising triodes 98 and 99 and diode I58. The cathode of tube 98 is connected to ground, and its plate is connected through a resistor NH and diode I98 in series to a suitable source of positive direct voltage. The control electrode of tube 98 is connected through a resistor I82 to a tap on a voltage divider comprising resistors I83.and I84 and also through resistor I82 to capacitor 9'1. Resistors I53 and H14 in series are connected between the source of positive voltage and ground. The plate of tube 99 is connected to the positive voltage source while its cathode is connected to ground through a resistor I05. The

cathode of tube 99 is also connected through a capacitor I95 to the cathode of diode I00. The plate of tube 98 is connected to ground through a capacitor I81 and is. also connected to the control electrode of tube 99.

Since the control electrode of tube 98 is normally positive relative to its cathode, the tube conducts maximum current so that there is a relatively large voltage drop across resistor .iIlI

Z and a relatively small yoltageacross capacitor Hi1. Whena negatiuepulseflfiis applied to the control electrode. of tube. 98, the conduction of. current. by this tube is reduced and. the. potential at its plate tendsto. rise. However, capacitor I01 opposes. this rise. in. potential so the plate potential can rise only as fast. as capacitor IBI charges.

through resistor IIU.

The rise. in plate potential of tube 98. also increases the potential at the control electrode of tube 99. Tube 9.9 acts as. a cathode. follower so that its cathode. potential increases by substantially the same amount as its. control electrode potential. This increase, in potential is transmitted through. capacitor I86 to the cathode of diode I and thus tends to. maintainthe voltage across resistor. It! constant so that constantcharging current flows to capacitor lIlI. This makes the rise in. plate potential. of tube 98. very linear, and since the potential. at the cathode of tube as follows. the potential at the plate of tube 98, a very linear sweep voltage is provided across resistor I05. The waveform of this voltage is illustrated at 38,, Fig. 10. At the end of pulse 96, the control electrode of tube 98 again becomes positive, tube 98 conducts current, and the plate potential of. this tube rapidly drops to its former value.

The sweep voltage is transmitted through capacitor I08 to a phase inverter comprising triode III). The cathode of tube ill] is connected to ground through resistor H i, and the plate is connected to the positive voltage source through resistor 1 I2. The control electrode of tube Iifiis connected to. capacitor I69, and is. also connected to a tap on cathode resistor I through resistor H3. Thevaluesoi resistors III and H2 are so related that changes in potential at the control electrodeof tube I10 cause changes inpotential at its cathode and at its plate which are substantially equal but of opposite polarity. Thus, if the control electrode of tube IIil becomes more positive, its cathode. also becomes more positive, but its plate becomes .lesspositive or more negative. The potential at the cathode is represented by curve 183, Fig. 1.0,. while the potential at theplate isrepresentedby curve. IIA. These potential changes at the cathode and plate of tube Iii] are. transmitted to respective horizontaldeflectingplates of the iconoscope through capacitors H5 and H6 and connections 66 and GI.

The other set of sweep circuits 4'! applies similar horizontal sweep potentials to the other iconoscope. However, since scanning. is to take place alternately in the two iconoscopes, the two sets of sweep potentials must alternate in time. This is accomplished by the fact that the two sweep circuits are triggered by voltages obtained from opposite halves of the synchronizing multivibrator so that when a positive synchronizing voltage is applied to one sweep circuit, a negative voltage is applied to the other, as is shown by curves 82 and 83, Fig. 10. The horizontal sweep potentials applied to the second iconoscope are represented by curves Ill and III Fig. 10.

Again referring to Fig. 6, a differentiator circuit comprising capacitor H9 and resistor I20-in series is connected between connection GI and ground, asshown. This circuit differentiates the changes in plate potential of tube I It and applies to the control electrode of a vacuum tube 12! a voltage having the waveform shown by cur ve I22, Fig. 10. Vacuum tube I21, with its cathode resistor 12 3 and its plate load resistor :24, is connectedes a. volta e amplifier so. that. theoct ntial: at its plate has the waveform iliustratedby QILIV I25..Fie. 10. .It. may benoted th t this potenti l has a relatively positive value durin the linear portion of. the. sweep voltages I08. and Ill and base; large relatively-negative value durin the return .:portions of the sweep voltages. The changes inthis. potential are. applied to the control. electrode of theiconoscope through capacitorlZfi and connectionand serve to cut ofi or blank.the electron beam of the iconoscopeduring thereturn sweep. Connection I2] isprovided from the plate of tube H0 to the delay circuits for purposes hereinafter explained- As the electron beam. is swept across themosaic of iconoscope 36. Fig. 3, electric. pulses are. pro.- duced as represented by curve I28, Fig. 10. Similar electric pulses, represented by curve I29, are produced by iconoscope 31. The initial pulse or pulses I39 which are of relatively short duration are produced as the electron beam strikes one edge of the mosaic. A relatively wide pulse I31 is produced as the beam travels across the partial optical image of the ingot, and a series of pulses I32 is produced as the beam crosses the other edge of the mosaic. i'he pulses represented by curves I28 and I23 are combined in the mixer circuit.

Referring now to Fig. 7, the mixer 49 comprises two vacuum tubes I33 and I38 which are prefcrablypentodes. Tubes i33-and- I34 are connected as cathode followers having cathode load resistors 35 and I36; respectively. The control electrodes of the two tubes are connected to taps on their respective cathoderesistors through resistors I37 and I38, as shown. The plates of the tubes are connected to a suitable source of positive direct voltage which may have a value of 180 volts, for example. The suppressor electrodes may be'connected to the cathodes, and the respective screen electrodes may be connected to the positive voltage source through resistors I39 and I46 and to the cathodes through capacitors MI and M2. Resistors I43 and M4 are connected in series between the two cathodes, and an output connection I45 is connected to the-circuit junction between these two resistors.

Electric pulses I28, Fig. 10, from iconoscope 36, Fig. 4, are applied to the control electrode of tube I33, Fig. 7, through. connection 69. Pulses I29 from iconoscope 31 are applied to the control electrode of tube I34 through connection I46. The twosets of pulses are combinedin the mixer, and both appear at output connection I45.

Referring now to Fig. 8,.delay circuits 5| comprise two diodes E47 and I48. Two voltage dividers comprising resistors M9, I50 and resistors I5], I52, respectively, are each connected between ground and a suitable source oi positive direct voltage, 300 volts, for. example. The plate of diode I4? is connected through resistor I53 to thecircuit iunctionbetween resistors I49 and I50, and. the plate of diode I48 is connected through resistor I54 to the circuit junction between resistors HI and E52. Two capacitors I55 and I56 are connected in series between the two diode plates, and a resistor I5! is connected be-- tween the circuit junction of these two capacitors .and ground.

"Voltage from sweep circuits 45, Fig. 6,. is appliedv to the cathode of vacuum tube I41, Fig. 8, through connection I2]. This voltage has a waveform illustrated by curve IN, "Fig; 10. Voltage having awaveform illustrated by curve 8, Fig. "10-, is-a-pplied to the cathode of tube 148,

9 Fig. 8, from sweep circuits 41 through connection I58.

Normally, the cathodes of tubes I41 and I48 are more positive than the plates and, therefore, the tubes do not conduct current. However, when sweep circuits 46 provide sweep potentials to the horizontal deflecting plates of iconoscope 36, the cathode of tube I41 becomes less positive, as illustrated by curve I I4, and at a certain point in such sweep determined by the bias potential at the plate of tube I81, the cathode of this tube becomes negative with respect to its plate, and the tube conducts current. The plate potential then follows the cathode potential during the remainder of the sweep. As a result, the plate potential of tube I41 has the same waveform as curve II except that the initial portion of the sweep is eliminated. This potential is diiferentiated by capacitor I55 and resistor I51 which thereby produces a waveform represented at I59, Fig. 10. A similar action occurs in diode I48 which produces the waveform illustrated at I66, Fig. 10. The combination of these two waveforms, which produces the complete curve I6I,

Fig. 10, appears at output connection I62, Fig;

8, which is connected to the circuit junction of capacitors I55 and I56.

Referring now to Fig. 9, which is a circuit diagram of indicator circuits 58, the output of the mixer is applied through connection I45 to a two-stage vacuum tube amplifier and differentiator circuit comprising vacuum tubes I63 and I64. The cathodes of tubes I63 and I64 are connected to ground through cathode resistors I65 and I66, and their plates are connected to a suitable source of positive direct voltage through load resistors I61 and I88, respectively. The control electrode of tube I63 is connected to ground through grid leak resist'or I69 and is connected to connection I45 through capacitor I10. The plate of tube I83 is connected to the control electrode of tube I64 through capacitor HI and resistor I12 in series. The circuit junction of capacitor HI and resistor I12 is connected through resistor I 13 to ground, and the control electrode of tube I64 is connected to ground through capacitor I14. This network of resistors and capacitors between the two vacuum tubes differentiates the voltage waveforms whereby the potential at the plate of tube I64 has the waveform illustrated by curve I15, Fig. 10.

The significant pulses in this waveform, curve I15, are the initial pulse I18 which is produced as the iconoscope electron beam crosses the first edge of the photosensitive mosaic, a pulse I11 which is produced when the electron beam first reaches the optical image focused on the mosaic, a pulse I18 produced when the electron beam first reaches the other end of the mosaic, and other pulses I19 produced as the beam'is swept beyond the limits of the photosensitive mosaic. The smaller pulses represent noise voltages inherently present. In this series of pulses, the average time interval between pulses I11 and I18 is related to the width of the ingot being measured. The other pulses are superfluous and should be blocked or otherwise removed as hereinafter explained. With this arrangement, pulses I13 are a fixed reference with respect to which the time position of pulses I11 is determined. An-

and I 8I in series to the control electrodeof a vacuum tube I82. The cathode of tube I82 is connected to a tap on a voltage divider comprising resistors I83 and I84 connected in series between a source of positive voltage and ground. The control electrode of tube I82 is connected to ground through a resistor I85. This system of connections maintains the control electrode of tube I82 greatly negative with respect to its cathode so that this tube normally conducts no current even when positive pulses I16 are applied to its control electrode from vacuum tube I64.

Voltages having the waveform shown by curve I6I, Fig. 10, are applied through connection I62 to the control electrode of a vacuum tube I86, Fig. 9. This vacuum tube is connected as a voltage amplifier with its cathode connected to ground through a resistor I81 and its plate connected to a source of positive voltage through a resistor I88. The plate of tube I86 is also connected through resistor I89 to the circuit junction between capacitors I86 and I8I. When negative voltage is applied to the control electrode of tube I86, the plate of this tube becomes more positive, and this in turn carries the control electrode of tube I82 positive. This reduces the negative bias of tube I82 sufiiciently for this tube to conduct current when positive pulses I11 and I18 are received from tube I64. Tube I82 thus acts as a gate under the control of voltage received through connection I62 from the delay circuits. Referring to curve I8I, Fig. 10, and'remembering that positive voltage is applied to the control electrode of tube I82 when the waveform of curve I9! has a negative value, it may be noted that tube I82 will not conduct current when pulse I16 arrives at its control electrode, and thus this pulse is blocked. However, the control electrode of tube I82 is at'a higher positive potential when pulses I11 and I18 arrive, and therefore these pulses are transmitted through the tube. The length of time in the initial portion of each sweep during which tube I82 blocks pulses can be adjusted by adjusting the tap voltages of votage dividers I49, I56 and I5I, I52, Fig. 8. A ortion of each divider may have an adjustable resistance value, as indicated in the drawing, for this purpose.

The plate of tube I82, Fig. 9, is connected to a source of positive direct voltage through a resistor I98. Each time tube I82 conducts current, there is a voltage drop acrossresistor I99 so that pulses I11, I18 and I19, Fig. 10, appear as negative pulses at the plate of tube I82. These negative pulses are transmitted through capacitor I9I to the'control electrode of vacuum tube I92.

The plate of tube I 92 is connected to the positive voltage source through a resistor I93. The

cathode of this tube is connected directly to ground, and the control electrode is connected to ground through resistor I94. Tube I92 normally conducts current, but when negative pulses from tube I82 are applied to the control electrode of tube I92, it is driven to cutoff, and pulses of uniform positive amplitude appear at its plate. Tube I92 thus acts as a clipper which clips all of the pulses to the'same amplitude. The pulses appearing at the plate of tube I92 are represented by curve I95, Fig. 10. Pulses I96 are produced as the electron beams of the iconoscopes first reach the optical images focused on the mosaics, pulses I91 are produced when the electron beams reach the edges of the mosaics, and pulses I 98 are produced as'the beams are swept past the edges of themosaics. p

Pulses I96 and "I91 are transmitted through capacitor I99,.resistor 208 and capacitor 28 I, connected in series, to the input connection 202 of a trigger circuit means comprising an Eccles- Jordan trigger circuit. Pulses I98 are blocked in a manner hereinafter described. Any negative pulses which may appear at the plate of tube 92 are removed by a clipping circuit comprising a resistor 253 connected between ground and the circuit junction of capacitor M9 and resistor 200 and a rectifier 204 connected between ground and the circuit junction of resistor 28!) and capacitor 20!. The polarity of rectifier 204 is such that it offers relatively little resistance to negative pulses and thus by-passes these pulses to ground but offers a much higher resistance to positive pulses.

The Eccles-Jordan trigger circuit comprises two triodes 295 and 266 having their plates connected to a positive direct voltage source through resistors 29'! and 208, respectively. The cathode of tube 205 is connected to a tap on a voltage divider comprising resistors 209 and 245 connected in serie between the source of positive voltage and ground, as shown. The cathode of tube 256 is preferably connected to this same tap of the voltage divider through an indicating instrument 2!! which preferably is responsive to average or D.-C. values of current. Instrument 2!! thus provides indications which are related to the average current conducted by tube 296. The control electrode of tube 285 is connected to the plate of tube 296 through a resistor BIZ and a capacitor 213 connected in parallel and is connected to ground through resistor 2M. The control electrode of tube 208 is connected to the plate of tube 265 through resistor 2 i5 and capacitor 2H5 connected in parallel, and is connected to ground through resistor 2M. Input connection 292 is connected to the control electrode of each vacuum tube through capacitors M8 and 2 [9, respectively.

As is well known, the Eccles-Jordan trigger circuit has two table operating states. In one such state, tube 205 conducts current, while tube 286 does not; and in the other state, tube 206 conducts current while tube 205 does not. Positive voltage pulses applied to the control electrodes of tubes 285 and 296 trigger "the Ecc1es Jordan circuit and cause it to shift from one onerating state to the other.

The pulses at input connection 202 have the form illustrated by curve 220, Fig. 10. The average time interval between pulses 22! and 222 is related to the width of the ingot being measured, as has been explained. Just before pulse 22! arrives, tube 285 is conducting current and tube 286 is not. Pulse 22! triggers the Eccles- Jordan circuit and causes it to switch to its other operating state in which tube 205 conducts current. Pulse 222 then triggers the circuit back to its original state. The length of time in each sweep cycle during which tube 295 conducts current, and hence the average or D.-C. value of current conducted by tube 206, is proportional to the average time interval between pulses 22! and pulses 222, and hence is related to the width .of the ingot being measured. Instrument 2!! gives an indication proportional to this average current. Instrument 2!! can be calibrated to provide direct readings in terms of ingot width when the two iconoscopes are spaced a predetermined distance apart, or in terms of deviation from a standard width corresponding to the spacing between the two iconoscopes.

The potential at the plate of tube 206 has a waveform illustrated by curve 22 3, Fig. 10. This waveform isdifierentiated by a capacitor 224 and a resistor 225, Fig. 9, to give the waveform illustrated by curve 226, Fig. 10, having pairs of voltage pulses 227 and 228 which are alternately positive and negative. Positive pulses 228 occur when the Eccles-Jordan circuit is triggered back to its first operating state in which tube 23% conducts current, and thus correspond to the end of a sweep cycle.

Positive pulses 225 trigger a cathode-coupled trigger circuit comprising vacuum tube 22?! and 230, Fig. 10. The cathodes of tubes 228 and 236 are connected together and are connected to ground through a common cathode resistor 23!. The plates of these tubes are connected to a positive direct voltage source through resistors 232 and 233, respectively. The control electrode of tube 230 is connected to a tap on a voltage divider comprising resistors 23 i and 225. The control electrode of tube 229 is connected to a tap on a voltage divider 235 through a resistor 236. The two voltage dividers are connected between ground and a source of positive direct voltage, as shown. The control electrode of tube 229 is also connected through a capacitor 23? to the plate of tub 230.

The circuit constants of this trigger circuit, are such that tube 229 normally conducts ciurent while tube 230 i normally cut off. When positive pulses 228 are applied to the control electrode of tube 230, the circuit is triggered so that tube 23!! becomes conductive and tube 229 is cut off. The control electrode of tube 223 is maintained sufficiently negative to keep this tube cut off until a sufiicient amount. of the charge on capacitor 23'! leaks off through resistor 235 for tube 229 to become conductive again, which triggers the circuit back to its original operating state. The length of time during which tube 229 i nonconducting, therefore, depends upon the circuit constants. The voltage waveform at the plate of tube 229 is represented by curve 238, Fig. 10.

The voltage represented by curve 233 is transmitted through capacitor 239, Fig. 9, to the con trol electrodes of two vacuum tubes 2-49 and 24! which comprise a clamping circuit which blocks undesired pulses. The plate of tube 250 is connected to a source of positive direct voltage. The cathode of tube 240 is connected to the plate of tube 24! and to input connection 222 of the Eccles-Jordan trigger circuit. The cathode of tube 24! is connected to a tap on a voltage divider comprising resistors 242 and 243 connected in series between the positive voltage source and ground. The cathode of tube 24! is also connected to ground through capacitor 244. The control electrodes of tubes 240 and 24! are connected together and are connected to ground through a resistor 245 and a rectifier 246 in parallel. The polarity of rectifier 258 is such that it offers relatively little resistance to current flow when the control electrode of tube 24! is at negative potential but presents a much larger resistance when the control electrode is at positive potential. This eliminates the possibility of any substantial negative potential appearing at the control electrodes of tubes 240 and 24!.

The control electrodes of tubes 2% and 24! are normally at ground potential while the cathodes of these tubes are substantially positive with respect to ground. Therefore, tubes 24d and 24! normally conduct no current and have no more effect upon. the circuit than would small capacitors .connected in their place' aevacrc However, when positive voltage is applied to the control electrodes of these two tubes, as it is during the positive portions of the curve 238 waveform, tubes 240 and 2M conduct current and the conductance of these two tubes thendetermines the potential of connection 202. In other words, tubes 240 and MI provide a low impedance path when they conduct current which effectively grounds any voltage pulses which would otherwise be transmitted by capacitor 20!. In this way the clamping circuit blocks the undesired pulses H38 in waveform I95, Fig. 10, and assures that the Eccles-Jordan trigger circuit will be in its :proper operating state ready to receive pulses 22] at the beginning of each sweep cycle.

Although satisfactory operation can be obtained without vertical deflection of the iconoscope electron beams, in general a larger signal from the iconoscopes, and hence greater overall sensitivity of the gauge to faint images, can be obtained by vertical scanning of the iconoscope mosaic at a rate which is rapid compared to the horizontal scanning so that, a relatively wide area of the mosaic is utilized instead of a single line. Referring again to Fig. 3, vertical scanning preferably is accomplished .by having a high frequency oscillator 24l'connected to supply high frequency alternating voltage to the vertical deflecting plates of each iconoscope. Oscillator 241 may be a conventional type which operates at a frequency in the order of one megacycle per second. These oscillations are transmitted to the vertical deflecting plates of iconoscope 36 through connections 66 and 61 and capacitors 64 and 65 and are transmitted to the vertical deflecting plates of iconoscope 31 through connections 248 and 249 and capacitors 250 and 25l.

When the object to be measured is a hot steel ingot, the brightness of the glowing ingot itself is sufficient to assure adequate contrast. between the ingot image and the background to properly operate the noncontacting width gauge. However, the gauge is not limited in use to self-luminous objects since a sufficient contrast between the image and the background can usually be obtained quite easily by illuminating the object to be measured, especially when rapid vertical scanning of the iconoscope mosaics is employed.

Having described the principles of this invention and the best mode in which I have contemplated applying those principles, I wish it to be understood that the apparatus described is illustrative only and that other means can be employed without departing from the true scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A noncontacting gauge for indicating the Width of an object, comprising a plurality of electron cameras each positioned to have the optical axis of the field of view thereof vertically aligned with a respective opposite edge of such object, for efiectively scanning the view of each of said cameras along a line extending in the direction of width of such object across the respective edge, whereby each of said camera provides an electric signal related to the position of the edge of such objects mixing circuit means operatively coupled to the output of both of said electron cameras for combining the electric signals of both cameras and thereby providing a composite electric signal related to the total width of such object, an electric signal responsive width-indi- '14 cating apparatus operativelyconnected to the output of said mixing circuit means in responsive relation to the signals so produced.

2. A noncontacting gauge for measuring the width of hot steel ingots, comprising two electron cameras each having a photosensitive mosaic and adapted to be positioned on opposite sides of the ingot, means to form a partial optical image of such ingot including only one of its edges upon the mosaic of one of said electron cameras, means to form a partial optical image of such ingot including only the opposite one of its edges upon the mosaic of the .other of said electron cameras, scanning means to provide scanning across the width of such partial images alternately, whereby said electron cameras produce relatively long electric pulses which are related in average duration to the total width of such ingot, mixer means coupled to each of said electron cameras for combining such pulses, a trigger circuit having two stable states of operation, means operatively connecting the output of said mixer means to said trigger circuit for triggering the-same from one of its operating states to the other at the be ginning and end of said electric pulses, first gating means synchronized with said scanning means to block pulses preceding the beginning of each scan, second gating means synchronized with said trigger circuit to block pulses following the ending of each scan, and a current responsive indicating device connected to'said trigger circuit in responsive relation to the current conducted during one of the operating states thereof.

3. A noncontacting gauge for indicating the width of an object comprising at least two electron cameras each having a photosensitivesurface and adapted to be positioned on opposite sides of the object, means to form a partial optical image of such object including one of its edges upon the photosensitive surface of one of said cameras, means to form a partial optical image of such object including the edge thereof opposite the first-mentioned edge upon the photosensitive surface of the other of said cameras, means to provide scanning across the-width of such partial images whereby electric pulses are produced which are related to the total width of such object, electric pulse responsive width in-,

dicating apparatus operatively connected to said cameras in responsive relation to the pulses so produced. and gating control means operatively connected to said indicating apparatus to prevent operation of the same by pulses other than those related to the width of the object being measured.

4. A noncontacting gauge for indicating the width of an object comprising a plurality of light sensitive electron-optic devices each positioned to View only a respective opposite edge of such object with the optical axis of the field of view of each electron-optics device being in vertical alignment with the respective edge of the object, means for effectively scanning the view of each of said electron-optics devices along a line extending in the direction of the width of such object across the respective edge whereby each electron-optics device provides an electric signal related to the position of the edge of such object, mixing circuit means operatively coupled to the output of all of said electron-optics devices for combining the electric signals of all the electron-optics devices and thereby producing a composite electric signal related to the total width of such object, and electric signal responsive width indicating means operatively connected to E the output of said mixingcircuit means for providing an indication of the total width of the object being viewed.

5. A noncontacting gauge for indicating the width of an object comprising a, pair of light sensitive electron-optic devices each positioned to view only a respective opposite edge of such object with the optical axis of the field of view of each electron-optics device being in vertical alignment with the respective edge of the object, means for effectively scanning the view of each of said electron-optics devices along a line extending in the direction of the width of such object, across the respective edge, whereby each electron-optics device provides an electric signal related to the position of the edge of such object, mixing circuit means operatively coupled to the output of both of said electron-optics devices for combining the electric signals of both devices and thereby provide a composite electric signal related to the total width of such object, and a current responsive indicating device operatively connected to the output of said mixing circuit means for providing an indication of the total width of the object being viewed.

6. A noncontacting gauge for indicating the width of an object comprising a pair of light sensitive electron-optics devices each positioned to view only a respective opposite edge of such object, means for efiectively scanning the view of each of said electron-optics devices along a line extending in the direction of the width of such object across the respective edge whereby each electron-optics device provides a pulsed electric signal related to the position of the edge of such object, trigger circuit means having two stable states of operation, means operatively coupling the output of said electron-optics devices to said trigger circuit means for efiectively triggering the same from one of the operating states thereof to the other with the pulsed electric signals produced by said electron-optics devices, and

" a current responsive indicating device coupled to the output of said trigger circuit means and responsive to the current conducted during one of the operating states thereof for providing an indication of the total Width of the object being viewed.

7. A noncontacting gage for indicating the width of an object comprising a pair of light sensitive electron-optics devices each positioned to view only a respective opposite edge of such object, means for effectively scanning the view of each of said electron-optics devices along a line extending in the direction of the Width of such object across the respective edge whereby each electron-optics device provides a pulsed electric signal related to the position of the edge of such object,- trigger circuit means having twostabie states of operation, means operatively coupling the output of said electron-optics devices to said trigger circuit means for effectively triggering the same from one of the operating states thereof to the other with the pulsed electric signals produced by said electron-optics devices, gating control means operatively coupled to said trigger circuit means to prevent operation of the same by pulsed electric signals other than those related to the position of the edges of the object being measured, and a current responsive indicating device coupled to said trigger circuit means and responsive to the current conducted during one of the operating states thereof for providing an indication of the total width of the object being viewed.

8, A non-contacting inspection gauge for strip material including in combination first electronoptics means having the optical axis of the field of view thereof vertically aligned with a respective longitudinally extending edge of the strip of material being gauged for producing a first series of electric pulses having durations which vary with variations in the position of said one longitudinally extending edge of the strip of material, second electron-optics means having the optical axis of the rfield of view thereof vertically aligned with the remaining longitudinally extending edge of thestrip of material for producing a second series of electric pulses having durations which vary with the variations in the position of the remaining longitudinally extending edge of the strip of material, electric signal commining means coupled to the output of both of said electron-optics means for combining said first and second series of electric pulses to pro duce a composite electric signal representative of the width of the material, and an indicating device operatively coupled to the output of said electric signal combining means for providing an indication of the width of the material.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,117,878 Friedmann May 17, 1938 2,237,811 Cockrell Apr. 8, 1941 2,240,722 Snow May 6, 1941 2,301,254 Carnahan Nov. 10, 1942 2,324,270 Schlesman July 13, 1943 2,447,024 Metcalf Aug. 17, 1948 2,474,906 Meloon July 5, 1949 2,488,430 Ofine'r Nov. 15, 1949 2,514,985 Banner July 11, 1950 2,548,755 Vossberg et a1 Apr. 10, 1951 

